The present invention relates to cards carrying magnetic strips, and in particular, to a code strip having physical interruptions, together with methods and apparatus for making and using such cards.
Credits cards and bank identification cards are commonly manufactured with a rear stripe magnetically encoded with a phase modulation technique. The coding can represent the user indentification number. An important consideration in the personalization of these cards is ensuring that the magnetic code cannot be reproduced or altered by counterfeiters. The capital investment needed to produce counterfeit or altered cards should be prohibitively high. Unfortunately, the conventional magnetic strip can be re-encoded with a relatively modest investment, making it economically attractive for the counterfeiter.
A card can be erased accidentally by the card owner himself and no simple technique exists for restoring readibility. Some card thieves can take advantage of this problem. The thieves may be concerned primarily with avoiding the step of having a stolen card read by a point-of-sale machine that verifies whether use of the card is permissible. By the simple expedient of passing a strong magnet near the stripe its magnetic code can be erased. Inattentive sales personnel may accept the card, assuming either an innocent erasure or that something is wrong with their card reading machine.
It has been proposed in the past to embed a series of separate magnetizable bars in a structure to represent an NRZ Code. However, this code has significant disadvantages. Furthermore, the concept of embedding separate magnetizable bars results in a structure that is difficult to manufacture, is not readable in existing machines, which are numerous and represent a large investment that will not be fully replaced. See U.S. Pat. No. 3,803,634.
Methods have been proposed to alternately magnetize a fluid medium which then parts at the transitions, due to the repelling magnetic forces, to form separate unmagnetized areas, which are then frozen. However, this system is difficult to manufacture, and has not proved suitable for producing various codes, such as phase modulaton. Also by requiring different magnetic orientations, additional complexity results. The pattern is not compatible with existing card readers.
Accordingly, there is a need for an improved magnetizable strip that is able to carry various codes, is readable in existing card readers, can encode individual card information--thus defeating mass use of stolen blank cards --, can have the encoded information easily restored to machine readibility, and is secure from alternation and forgery. It is also desirable that any adjacent tracks carrying termpoary information (such as account balance) can still be read and re-written, in a form compatible with existing equipment.